The present invention relates to taste masked compositions for bitter drugs, comprising a combination of two enteric polymers, such as a methacrylic acid copolymer, and a phthalate polymer. It also relates to a process for preparing such a composition.
For ease and safety of administration, most drugs are formulated as tablets or capsules for oral administration. However, patients at the extremes of age, such as children and the elderly, often experience difficulty in swallowing solid oral dosage forms. For these patients, drugs are commonly provided in liquid dosage forms such as solutions, emulsions and suspensions. These dosage forms usually permit perceptible exposure of the active drug ingredient to the taste buds, which can be a problem when the drugs have an unpleasant taste or are extremely bitter. Conventional taste masking techniques such as the use of sweeteners, amino acids and flavoring agents are often unsuccessful in masking the taste of highly bitter drugs and other techniques have been and continue to be exploited for the effective taste masking of such drugs. Extremely bitter drugs, like, quinine, ciprofloxacin, clarithromycin, cefuroxime axetil, can now be formulated as a fairly acceptable range of products even for pediatric use, which through conventional techniques would be impossible to formulate.
Use of cationxe2x80x94exchange resins (such as polysulfonic acid and polycarboxylic acid polymers) to adsorb amine drugs for taste masking and sustained release has been reported to have limited applicability and is not capable of masking the taste of highly bitter drugs. Coating of bitter drugs is another method which has been reported for taste masking. This technique alone may prove effective for moderately bitter drugs or in products where the coated particles are formulated as aqueous preparations before administration or are formulated in a non-aqueous medium. This technique has its limitations as coating of fine particles is usually technology intensive and coated granules are readily ruptured by chewing and compression.
Lipid-based microencapsulation is another technique used to taste mask the drugs. This technique requires highly sophisticated hot-melt granulation for producing fine particles, and may have adverse effects on heat sensitive molecules or restrict drug release adversely. U.S. Pat. No. 4,865,851 describes cefuroxime axetil in particulate form coated with an integral coating of lipid or a mixture of lipids.
U.S. Pat. No. 4,808,411 describes a taste-masked composition comprising 95% of erythromycin or a derivative thereof and about 5 to about 75% of a carbomer. The drug and carbomer are believed to be held together by both the ionic interactions between the amine group of erythromycin compound and the carbonyl group of the carbomer and by the gel properties of the carbomer. This complex is further taste masked by coating. Although use of this complexing technique, optionally with a coating, has evolved into a useful technique for taste-masking, proper selection of the complexing agent is vital such that in trying to achieve taste-masking, drug release is not compromised.
U.S. Pat. No. 5,286,489 describes a porous drug-polymer matrix formed by admixing one or more bitter tasting active ingredient and a methyl methacrylic ester copolymer in at least a 1:1 by weight ratio of active ingredient to copolymer, effective to mask the taste of the drug. None of the examples described in this patent disclose the effect of these polymers on the release of the drug from the matrix. It has been our experience that although the drug-polymer matrix formed following the teachings of this patent results in good taste-masking, it also retards the rate of drug release from the matrix to an extent which would be unacceptable for a conventional immediate release formulation. Following the teachings of this patent, only 42% of cefuroxime axetil was released from the matrix in 45 minutes in media of pH greater than 4.0. The matrix described in this patent is therefore unsuitable for drugs which are absorbed at a pH range greater than 4.0. To enhance the release of the drug, an enteric phthalate polymer was added into the matrix without significantly compromising on the taste masking.
Accordingly, none of the references heretofore described is completely satisfactory for various reasons.
The object of the present invention is to provide a taste masked composition, which effectively masks the taste of the drug without compromising the dissolution rate, comprising a bitter tasting drug and a combination of two enteric polymers comprising a methacrylic acid copolymer and a phthalate polymer.
A further object of the present invention is to describe a process for the preparation of a taste masked matrix comprising the process of dissolving the bitter tasting drug, a methacrylic acid copolymer and a phthalate polymer, in a suitable organic solvent followed by the recovery of said taste masked matrix from the solution thereof.
The taste masked composition of the present invention comprises a bitter tasting active, and two enteric polymers wherein the enteric polymers are a methacrylic acid copolymer and a phthalate polymer. Examples of bitter or unpleasant tasting drugs which may be used, include, but are not limited to, macrolide antibiotics, such as erythromycin and clarithromycin, fluoroquinolones such as ciprofloxacin and norfloxacin, cephalosporins such as cefuroxime and ceftriaxone, tetracyclic antibiotics like chloramphenicol, chlorpromazine etc. The drug itself or its pharmaceutically acceptable salt or ester may be used in the present invention.
The methacrylic acid copolymers used according to the present invention, may include methylmethacrylic ester copolymers, such as Eudragit S and Eudragit L (trademark of Rohm Pharma) and copolymers of ethyl acrylate and methacrylic acid as Eudragit L-100-55 (trademark of Rohm Pharma). The phthalate polymers include cellulose acetate phthalate, ethyl vinyl phthalate, polyvinyl acetate phthalate and hydroxy alkyl cellulose phthalates. This combination of the two enteric polymers, methacrylic acid copolymer and a phthalate polymer results in optimal taste-masking and dissolution characteristics of the drug. The ratio of methacrylic acid copolymer to phthalate polymer can be varied from 1:9 to 9:1 depending upon intensity of bitterness and desired release of the active ingredient. Most preferably the two polymers are in the ratio of 1:1.
Preferably for optimal taste masking effect, total polymer to drug ratio is at least 1:4.
According to the present invention, the taste masked matrix described above, is prepared by dissolving, optionally with heating, the bitter active ingredient, a methacrylic acid copolymer and a phthalate polymer in a solvent system and then recovering the matrix including the active ingredient and the two polymers from the solution thereof. The solvent system chosen is one in which, both the active ingredient and the polymers are either soluble or swellable. Preferred solvents include water, ketones such as acetone, alcohols such as ethanol, esters such as ethyl acetate and their mixtures. The matrix is recovered by conventional methods which include vacuums evaporation, tray drying, spray drying, and drum or belt film drying. Spray drying is the preferred method for solvent removal. The xe2x80x9csolid solutionsxe2x80x9d thus formed keep the drug in a finely dispersed state within the polymers, preventing the exposure of the bitter tasting drug to the taste buds.
The process of spray drying gives highly porous material which can be further compacted to granules to improve the taste masking effect. The porosity of the granules thus obtained, is not only important for dissolution but also determines the extent of taste masking.
Channeling agents can be used to further tailor the drug release from the compacted granules. Channeling agents help in opening up the granules in a specific media as desired. The channeling agents include, disintegrants like croscarmellose sodium, crospovidone and sodium starch glycolate, diluents such as lactose, mannitol, sodium chloride, talc, polyvinyl pyrrolidone; gelling agents like carbopol, and xanthan gum, among others.
The taste masked granules obtained may be mixed with flavoring agents such as natural or artificial flavors, citric and tartaric acids, sweeteners such as saccharin and aspartame, and with other pharmaceutically acceptable excipients to be formulated as conventional whole, chewable or disperseible tablets, dry syrups, suspensions, sachets or any other suitable oral dosage forms.
The use of particle coating offers additional taste masking on the product. The coating composition can be constituted of either pH dependent or pH independent polymers depending on desired product characteristics. Coating compositions such as that described in our PCT application No. PCT/IB99/01735 (which is incorporated herein by reference) offer additional advantages as they can effectively mask the remaining bitterness of the drug without significantly affecting its dissolution profile. Other coating polymers such as the cellulosic polymers and methacrylic acid copolymers may also be used to optimize the taste masking effect.